Cleaning new masonry is easiest if you take some simple precautions during construction. Even with these precautions, a few accidental mortar smears and splatters are probably inevitable. But mortar stains can be removed without leaving a permanent discoloration. CLEANING CONCRETE MASONRY For concrete masonry, let large mortar droppings harden slightly, then remove them with a trowel, putty knife, or chisel. Block surfaces also may be rubbed with another small piece of block, then with a stiff fiber-bristle or stainless steel brush. The National Concrete Masonry Association (NCMA) does not recommend any other cleaning methods. Don't use acid solutions to clean concrete masonry. CLEANING CLAY BRICK For clay masonry, use wooden paddles, nonmetallic scrapers, or chisels to remove large particles of fresh mortar. For small splatters, stains, or the residue from larger pieces, brush the surface with a medium-soft fiber-bristle brush. Mud, dirt, or soil can be washed away using a detergent solution. VANADIUM STAINS Don't apply any type of cleaning agent other than water to light-colored brick (buff, pink, tan, white, or gray) or red brick without consulting the brick manufacturer. Acid solutions in particular can sometimes cause green or yellow vanadium stains on these units. MANGANESE STAINS Manganese compounds are sometimes used as coloring agents in tan or brown brick. If brick masonry is cleaned with an acid solution, these compounds can be leached out of the brick. This causes an oily brown stain. To remove manganese stains, use a proprietary cleaning compound or mix a solution of acetic acid, hydrogen peroxide, and water in a 1:1:6 proportion by volume.